This invention relates to a heat exchanger, more particularly but not exclusively to a shell and tube heat exchanger.
A known shell and tube heat exchanger comprises a cylindrical container with parallel tubes extending between two end baffles in the container so that a first fluid can pass through the tubes from one side of one end baffle to past the other baffle. Meanwhile, a second fluid flows in and through the space between the two end baffles so as to come into contact with the tubes. To give best heat exchange between the two fluids, the flow of the second is controlled by intermediate baffles which define respective non-aligned passages so the second fluid has to change direction in passing from one passage to the next. The intermediate baffles could comprise annular rings and discs so the second fluid has to change direction radially from one to the next of they could comprise disc segments so the flow of the second fluid is segmental.
With both forms of flow, i.e. radial and segmental, the second fluid has to change direction several times along the length of the shell. This causes a reduction in the dynamic pressure of the second fluid, which can, in turn, adversely effect the performance of the heat exchanger.
It is an object of the present invention to reduce the effects of the above disadvantages and generally provide a heat exchanger of improved construction and with improved heat exchange characteristics.
In accordance with a first aspect of the invention, a shell and tube type heat exchanger comprises a tubular shell containing a spiral baffle path defined by a spiral baffle through which a tube bundle extends in a direction generally parallel with the longitudinal direction of the tubular shell, the heat exchanger comprising an assembly of a plurality of heat exchange elements each of which comprises a shell section to form part of the axial length of the shell and a spiral section to form part of the length of the spiral baffle path.
The shell and baffle sections of the or at least some of the heat exchange elements may be integrally formed, e.g. by casting or moulding.
A spiral baffle section may be secured to, or integrally formed with, e.g. by casting or moulding, a central member, for example, in the form of a rod or tube and each element may include said central member.
A plurality of heat exchange elements assembled in series to form a heat exchanger may be united by, for example, welding or by bonding with adhesive.
The spiral section may be in the form of a single curved sheet which executes one or more complete turns around the inner surface of the shell section. The spiral baffle section may be in the form of several curved sheets, each one of which executes one turn or the same whole number of turns around the inner surface of the length of the shell.
The heat exchanger may comprise a plurality of identified heat exchange elements. The shell sections may be, for example, of circular or square shape as seen in plan view.
In accordance with a second aspect of the invention a shell and tube heat exchanger comprises a cylindrical shell, two tube plates, and a tube bundle supported by the tube plates, a region of the shell located between the tube plates and extending around the whole periphery thereof being inwardly or outwardly deformed and allowing differential expansion between the shell and the tube bundle.
Said cylindrical shell may be defined by the outer regions of a plurality of heat exchange elements as described herein and arranged in series.
In accordance with a yet further aspect of the invention there is provided a heat exchange element for a modular type heat exchanger, said element comprising a shell section to form part of the axial length of a shell and a spiral section to form part of a spiral baffle path.